Au-Ga-In Brazing Material

ABSTRACT

A brazing material which can be melted at a suitable temperature at which damage is not given to a device inside a package upon sealing, and besides the brazing material is not remelted, e.g., upon mounting to a board, and which has a low temperature difference between a liquid and a solid. The brazing material is made of a Au—Ga—In ternary alloy, wherein weight concentrations of the elements lie within a region of a polygon with a point A (Au: 90%. Ga: 10%, In: 0%), a point B (Au: 70%, Ga: 30%, In: 0%), a point C (Au: 60%. Ga: 0%. In: 40%) and a point D (Au: 80%, Ga: 0%. In: 20%) as vertexes. excluding lines on which In and Ga become 0%, in a Au—Ga—In ternary phase diagram.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a brazing material and a sealing methodusing the brazing material. In particular, the present invention relatesto a brazing material used for hermetically sealing a package forvarious electronic components. The present invention provides a brazingmaterial which is not remelted, e.g., upon mounting to a board withoutgiving damage to a device inside the package upon sealing and hassuitable properties.

2. Description of the Related Art

Electronic components such as an SAW filter and a crystal oscillatorused in various types of electronic equipment such as a cellphone arehermetically sealed in a package made of ceramics or the like in view ofprotecting an internal device. A brazing material for sealing thepackage has progressively been made lead-free in view of recentenvironmental protection. In this view, a Au—Sn brazing material(particularly, a Au-20 wt % Sn brazing material having an eutecticcomposition) is generally used (Patent Document 1). An advantage of theAu—Sn brazing material is that the Au—Sn brazing material enables anefficient sealing operation upon sealing the package since the Au—Snbrazing material has a comparatively low melting point of about 280° C.

Patent Document 1: Japanese Patent Application Laid-Open No. 2001-150182

Although the Au—Sn brazing material has preferable properties upon thesealing operation of the package, the Au—Sn brazing material also has aproblem. The problem is caused when the sealed package is mounted to aboard. Since a temperature upon mounting is close to the melting pointof the Au—Sn brazing material, the heat remelts the brazing material tocause peeling and leak of the sealed part of the package. Anotherproblem to be concerned about, other than the case where the package ismounted to the board, is that when the board is heated to collectdamaged parts in repairing the electronic equipment, the heat may breakthe sealing of other non-damaged parts.

The remelting of the brazing material is caused by the low melting pointof the brazing material. Then, brazing materials having somecompositions have been proposed in consideration of the problem. Forexample, Patent Document 2 proposes the application of a Au—Ge brazingmaterial, particularly a Au-12.5% Ge brazing material. The Au—Ge brazingmaterial has a melting point exceeding 360° C. Patent Document 3proposes a brazing material made of a ternary alloy of Au, Ge and Sn.

Patent Document 2: Japanese Patent Application Laid-Open No. 7-151943

Patent Document 3: Japanese Patent Application Laid-Open No. 2007-160340

Both the Au—Ge brazing material and the Au—Ge—Sn brazing material have amelting point higher than that of the Au—Sn brazing material. Theremelting of the brazing materials having a comparatively high meltingpoint after sealing may be reduced.

However, the Au—razing material tends to have an excessively highmelting point. Considering the melting point, a sealing temperature mustbe set to 400° C. or more. The sealing performed in the high temperatureatmosphere increases the thermal damage of a device inside the package,and may possibly damage the element.

On the other hand, it can be said that the Au—Ge—Sn brazing materialminimizes the problem of the damage to the composition upon sealingsince the Au—Ge—Sn brazing material has a melting point suppressed to alevel lower than that of the Au—Ge brazing material. However, ternaryalloys such as the Au—Ge—Sn brazing material may cause a problem of atemperature difference between a liquidus and a solidus. How large orsmall the temperature difference between the liquidus and the solidusaffects workability upon sealing the package. In Patent Document 3, thetemperature difference is set to be less than 50° C. However, it ispreferable if the temperature difference is small.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention has been made against the above-describedbackground. The present invention provides a brazing material which canbe melted at a suitable temperature at which damage is not given to adevice inside a package upon sealing, and besides the brazing materialis not remelted, e.g., upon mounting to a board, and which has a smalldifference in temperature between a liquidus and a solidus.Specifically, the present invention provides a brazing material whereinthe liquidus and/or the solidus exceed 280° C. and is 360° C. or less(preferably, both the liquidus and the solidus are within a range of 300to 340° C.), and a difference between the liquidus and the solidus isless than 45° C. (preferably, less than 40° C.).

SUMMARY OF THE INVENTION

The present inventors have studied the application of a brazing materialmade of Au, Ga and In as constituent elements and made of a ternaryalloy in which Au, Ga and In are alloyed, for solving theabove-mentioned problems. The present inventors have found a brazingmaterial having a prescribed composition range, and have hit upon thepresent invention.

That is, the present invention is a brazing material comprising aAu—Ga—In ternary alloy, wherein weight concentrations of the elementslie within a region of a polygon with a point A (Au: 90%, Ga: 10%, In:0%), a point B (Au: 70%, Ga: 30%, In: 0%), a point C (Au: 60%, Ga: 0%,In: 40%) and a point D (Au: 80%, Ga: 0%, In: 20%) as vertexes (excludinglines on which In and Ga become 0%), in a Au—Ga—In ternary phasediagram.

The ternary phase diagram showing the composition of the materialaccording to the present invention is shown in FIG. 1. The ternary alloyis applied in the present invention since the melting point of theternary alloy can be adjusted more effectively than a binary Au alloy(Au—In, Au—Ga) by simultaneously adding two elements of Ga and In to Au.The melting point (the liquidus, the solidus) can be set within asuitable range by setting the added amount of Ga and In to the rangewithin the region. The composition adjustment can also moderately reducea temperature difference between the liquidus and the solidus. Thebrazing material of the composition range can be made suitable even inprocessability and hardness.

In order to make hardness more suitable in addition to the melting pointof the brazing material, the temperature difference between the liquidusand the solidus, and processability, it is preferable that the weightconcentrations of the elements of the brazing material made of theAu—Ga—In ternary alloy lie within a region of a polygon with a point E(Au: 86%, Ga: 13%, In: 1%), a point F (Au: 81%, Ga: 17%, In: 2%), apoint G (Au: 79%, Ga: 10%, In: 11%) and a point H (Au: 84%, Ga: 6%, In:10%) as vertexes, in the Au—Ga—In ternary phase diagram. It is morepreferable that the weight concentrations of the elements of theAu—Ga—In ternary alloy lie within a region of a polygon with a point I(Au: 85%, Ga: 10%, In: 5%), a point J (Au: 80%, Ga: 14%, In: 6%), apoint G (Au: 79%, Ga: 10%, In: 11%) and a point H (Au: 84%, Ga: 6%, In:10%) as vertexes, in the Au—Ga—In ternary phase diagram. Specificexamples thereof include a brazing material lying within a range shownin a ternary phase diagram of FIG. 2.

The ternary brazing material according to the present invention maycontain at least one addition element of Sn, Ge, Zn, Sb, Si, Bi and Al.These addition elements are added in order to finely adjust the meltingpoint of the brazing material and improve the wettability of the brazingmaterial. The content of the addition element is preferably 0.001 to3.0% by weight, more preferably 0.01 to 3.0% by weight, and still morepreferably 0.1 to 3.0% by weight.

It is preferable that the brazing material according to the presentinvention has a material structure having a rapidly solidified structureformed from a molten state. It is because the material structure havingfine crystal grains formed by rapid solidification improves wettability.The relationship between the rapidly solidified structure and theimprovement of the wettability is not obvious. However, in this way,wetting spread tends to be improved upon being melted without changingmelting properties such as the liquidus and the solidus. A cooling ratefor obtaining the rapidly solidified structure is preferably set to 2000to 5000° C./min.

The brazing material according to the present invention can be used inany of plate, foil, grain, ball, powder and paste forms. For example, inorder to use the brazing material in the ball form, the same method asthat of the general brazing material can be used. The brazing materialcan also be used in a window frame shape, considering the shape of apackage member to be sealed. The brazing material according to thepresent invention can be manufactured by a casting method as in a usualAu alloy without particular difficulty. The brazing material can beprocessed in the plate and foil forms by rolling and punching or thelike if needed. The obtained rolled material can be subjected to presspunching and slitting without particular difficulty. Prescribed shapessuch as a ring shape and a ribbon shape can be obtained.

Furthermore, the brazing materials of the grain and ball forms can bemanufactured from a molten state by an atomization method, a rotatingelectrode method, a granulation in oil method and a liquid dropletspraying method or the like. As described above, in order to obtain therapidly solidified structure for improving the wettability of thebrazing material, the brazing materials of the plate and foil forms canbe manufactured by solidification using a cooling casting mold. Thebrazing materials of the grain and ball forms can be manufacturedaccording to manufacturing conditions (adjustment of the diameter of aliquid droplet, or the like).

The brazing material according to the present invention is suitable forhermetically sealing the package member. Although the sealing packagemember has a base accommodating a cap (lid) serving as a lid body and adevice, any of the cap and the base is preferably provided with thebrazing material made of the alloy according to the present invention.When the brazing material is fixed to the package member, the brazingmaterial is placed on the member, and the brazing material is melted andsolidified in a heating atmosphere to be fused. Kovar (an Fe—Ni—Coalloy) and 42 alloy (an Fe—Ni alloy) are generally used as the materialof the cap of the package member. Ceramic is used as the material of thebase. When the brazing material is fused, a fusing surface is previouslysubjected to Ni plating and/or Au plating from the object of improvingthe wettability of the brazing material, or the like. The brazingmaterial according to the present invention can also be fused to thepackage member previously provided with these plating layers.

In a method for hermetically sealing a package using the brazingmaterial and the package member according to the present invention, thepackage member is preferably joined with a sealing temperature being360° C. or more and less than 400° C., and preferably 380° C. or less.

ADVANTAGE OF THE INVENTION

As described above, the brazing material according to the presentinvention has suitable melting properties, and is suitable for sealingthe package. The brazing material has the improved temperaturedifference between the liquidus and the solidus, and has excellentworkability. The brazing material according to the present inventionalso has good processability, and can also be processed into a brazingmaterial for a package requiring downsizing and slimming down.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a Au—Ga—In ternary phase diagram showing a composition of amaterial according to the present invention;

FIG. 2 is a Au—Ga—In ternary phase diagram showing a preferablecomposition and a more preferable composition of a material according tothe present invention; and

FIG. 3 is an evaluation diagram of wettability of a Au—Ga—In ternarybrazing material (Au: 82%, Ga: 10%, In: 8%).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention and comparativeexample will be described. In this embodiment, a brazing material madeof a Au—Ga—In alloy having various compositions lying within and out ofa region of FIG. 1, and a brazing material in which Sn was added to aAu—Ga—In alloy were manufactured. The properties of the brazingmaterials were considered. In manufacture of samples, metals weighed soas to have a prescribed composition were melted, cast, and subjected torolling to produce brazing materials having a thickness of 50 μm.

The manufactured brazing materials were first evaluated for hardness,processability and melting properties (liquidus, solidus). The brazingmaterials were evaluated for the hardness with a Vickers hardness meter.The processed brazing materials were evaluated for the processability byobserving the existence or nonexistence of occurrence of break and crackof the brazing materials with a stereoscopic microscope (10 times). Thebrazing materials having no break and crack and capable of beingprocessed were evaluated as good. The brazing materials having observedbreak or crack were evaluated as poor. The melting properties weremeasured by differential thermal analysis. These results are shown inTable 1. This evaluation was also performed for Au—Ga (15.2%) which didnot contain In for contrast (sample No. 12).

TABLE 1 Melting properties Difference between liquidus and Composition(wt %) Hardness Solidus Liquidus solidus No. Au Ga In Sn (Hv)Processability (° C.) (° C.) (° C.) 1 84 13 3 — 242 good 304 317 13 2 8210 8 — 267 good 306 322 16 3 83 10 7 — 290 good 306 321 15 4 81 10 9 —292 good 306 323 17 5 82 11 7 — 300 good 306 324 18 6 83 9 8 — 301 good306 323 17 7 81.95 10.00 8.00 0.05 292 good 306 320 14 8 81.19 9.90 7.920.99 300 good 282 302 20 9 67 25 8 — 180 good 390 462 72 10 65 18 17 —224 good 380 418 38 11 62 13 25 — 257 good 383 408 25 12 84.8 15.2 0 —210 good 339 358 19

Table 1 shows that both the solidus and the liquidus of Au—Ga—In brazingmaterials (samples 1 to 6) having compositions lying within a region ofFIG. 1 are within a range of 300 to 340° C., and furthermore exhibitextremely excellent melting properties since the difference between thesolidus and the liquidus is less than 20° C. These brazing materials arepredicted to have a small difference with a sealing temperature uponsealing a package. It is thought that the brazing materials are mostsuitable as a brazing material for sealing the package. Particularly,the brazing materials of the samples 2 to 6 provide a result of havingalso sufficient hardness in addition to excellent melting properties. Onthe other hand, Table 1 shows that samples 9 to 11 having compositionslying out of the region of FIG. 1 have a high solidus and liquid us, andthe difference between the solidus and the liquidus is also large. Sincethe Au—Ga brazing material (sample 12) which does not contain In has acomposition close to an eutectic composition, the Au—Ga brazing materialhas a narrow difference between the solidus and the liquidus. However,since the Au—Ga brazing material has a high melting point, it cannot besaid that the Au—Ga brazing material is suitable.

On the other hand, there was observed an effect of notably reducing amelting point without extending the difference between the liquid us andthe solidus of the melting point by adding Sn from a result ofevaluating brazing materials (samples 7 and 8) to which Sn was added asan addition element. This reduction effect of the melting point wasobserved not only when Sn was added but also when at least one additionelement of Ge, Zn, Sb, Si, Bi and Al was added.

FIG. 3 shows a result of evaluating wettability of the ternary brazingmaterial (Au=82%, Ga: 10%, In: 8%) of the sample 2. The wettability wasevaluated by putting a brazing material on Kov/Ni plating/Au plating,heating the brazing material to a temperature 20° C. higher than amelting point under an inactive atmosphere, and holding the brazingmaterial for 2 minutes to be melted. When the brazing material portionwas wholly and homogeneously wet-spread, the brazing material wasdetermined as good. When the brazing material portion was notwet-spread, the brazing material was determined as poor. The resultshows that the brazing material portion is wholly and homogeneouslywet-spread, and the brazing material exhibits good wettability.

INDUSTRIAL APPLICABILITY

There can be provided a brazing material which can be melted at asuitable temperature at which damage is not given to a device inside apackage upon sealing, and besides the brazing material is not remelted,e.g., upon mounting to a board, and which has a small temperaturedifference between a liquidus and a solidus.

Au—Ga-—In Brazing Material

The brazing material according to the present invention is suitable forhermetically sealing the package member. Although the sealing packagemember has a base accommodating a cap (lid) serving as a lid body and adevice, any of the cap and the base is preferably provided with thebrazing material made of the alloy according to the present invention.When the brazing material is fixed to the package member, the brazingmaterial is placed on the member, and the brazing material is melted andsolidified in a heating atmosphere to be fused. Kovar (an Fe—Ni—Coalloy) and 42 alloy (an Fe—Ni alloy) are generally used as the materialof the cap of the package member pact. Ceramic is used as the materialof the base. When the brazing material is fused, a fusing surface ispreviously subjected to Ni plating and/or Au plating from the object ofimproving the wettability of the brazing material, or the like. Thebrazing material according to the present invention can also be fused tothe package member previously provided with these plating layers.

1. A brazing material comprising a Au—Ga—In ternary alloy, whereinweight concentrations of the elements lie within a region of a polygonwith a point A (Au: 90%, Ga: 10%, In: 0%), a point B (Au: 70%, Ga: 30%,In: 0%), a point C (Au: 60%. Ga: 0%, In: 40%) and a point D (Au: 80%,Ga: 0%, In: 20%) as vertexes, excluding lines on which In and Ga become0%, in a Au—Ga—In ternary phase diagram.
 2. The brazing materialaccording to claim 1, wherein the weight concentrations of the elementsof the Au—Ga—In ternary alloy lie within a region of a polygon with apoint E (Au: 86%, Ga: 13%, In: 1%), a point F (Au: 81%, Ga: 17%, In:2%), a point G (Au: 79%, Ga: 10%, In: 11%) and a point H (Au: 84%, Ga:6%, In: 10%) as vertexes, in the Au—Ga—In ternary phase diagram.
 3. Thebrazing material according to claim 1, wherein the weight concentrationsof the elements of the Au—Ga—In ternary alloy lie within a region of apolygon with a point I (Au: 85%, Ga: 10%, In: 5%), a point J (Au: 80%,Ga: 14%, In: 6%), a point G (Au: 79%. Ga: 10%, In: 11%) and a point H(Au: 84%, Ga: 6%, In: 10%) as vertexes, in the Au—Ga—In ternary phasediagram.
 4. The brazing material according to claim 1, furthercomprising at least one addition element of Sn, Ge, Zn, Sb, Si, Bi andAl.
 5. The brazing material according to claim 4, wherein an addedamount of the addition element is 0.001 to 3.0% by weight.
 6. Thebrazing material according to claim 1, wherein the brazing material hasa material structure having a rapidly solidified structure formed from amolten state.
 7. A hermetic sealing member part comprising the brazingmaterial according to claim
 1. 8. A sealing method comprising brazingcomponents with the brazing material according to claim
 1. 9. Thebrazing material according to claim 2, wherein the weight concentrationsof the elements of the Au—Ga—In ternary alloy lie within a region of apolygon with a point I (Au: 85%, Ga: 10%, In: 5%), a point J (Au: 80%,Ga: 14%, In: 6%), a point G (Au: 79%. Ga: 10%, In: 11%) and a point H(Au: 84%, Ga: 6%, In: 10%) as vertexes, in the Au—Ga—In ternary phasediagram.
 10. The brazing material according to claim 2, furthercomprising at least one addition element of Sn, Ge, Zn, Sb, Si, Bi andAl.
 11. The brazing material according to claim 3, further comprising atleast one addition element of Sn, Ge, Zn, Sb, Si, Bi and Al.
 12. Thebrazing material according to claim 9, further comprising at least oneaddition element of Sn, Ge, Zn, Sb, Si, Bi and Al.
 13. The brazingmaterial according to claim 10, wherein an added amount of the additionelement is 0.001 to 3.0% by weight.
 14. The brazing material accordingto claim 11, wherein an added amount of the addition element is 0.001 to3.0% by weight.
 15. The brazing material according to claim 12, whereinan added amount of the addition element is 0.001 to 3.0% by weight. 16.The brazing material according to claim 2, wherein the brazing materialhas a material structure having a rapidly solidified structure formedfrom a molten state.
 17. The brazing material according to claim 3,wherein the brazing material has a material structure having a rapidlysolidified structure formed from a molten state.
 18. The brazingmaterial according to claim 4, wherein the brazing material has amaterial structure having a rapidly solidified structure formed from amolten state.
 19. The brazing material according to claim 5, wherein thebrazing material has a material structure having a rapidly solidifiedstructure formed from a molten state.
 20. The brazing material accordingto claim 9, wherein the brazing material has a material structure havinga rapidly solidified structure formed from a molten state.